1. Field of the Invention
The present invention relates to well characterisation. In particular, but not exclusively, it relates to characterisation of a well using distributed temperature sensor (DTS) data to optimise a well model to determine physical parameters that characterise the well. Such a well may, for example, be a production well that can be exploited to produce oil and/or gas.
2. Description of Related Art
Much work has been undertaken by the oil and gas industry in the quest to obtain information that can determine physical parameters that characterise wells in order to provide for efficient production management. For example, a great deal of effort has been expended in providing monitoring equipment that can detect when problems occur during fluid extraction from a well and thereby warn an operator of an abnormal operating condition.
Many types of monitoring equipment using various techniques for measuring physical parameters that characterise wells are known. For example, the temperature profile of the well is one such physical parameter that can provide a well operator with useful information to characterise the well. One technique to obtain a temperature profile employs a downhole optical fibre acting as a DTS. A benefit of using such a DTS is that temperature data can be obtained continuously for the whole of the well without disturbing the flow of fluid from the well. By way of illustration, an example of a method and apparatus for determining flow rates employing a DTS system is described in U.S. Pat. No. 6,618,677, which is incorporated herein by reference.
By providing monitoring equipment that can warn an operator of abnormal operating conditions (such as, for example, where a well produces water rather than oil), the operator may take remedial action to account for the abnormal operating condition. For instance the operator may, upon detecting that water rather than oil is being produced, decide to shut down well production in order to attend to the cause of the abnormal operating condition. In this way, the monitoring equipment aids an operator in managing production.
However, while monitoring equipment exists that can aid an operator in managing production, such monitoring equipment tends only to provide an indication of the abnormal operating condition to the operator once the event has already happened. Thus, this type of monitoring equipment only enables the operator to provide a reactive response to the abnormal operating condition. Moreover, the monitoring equipment may not provide an accurate indication of exactly where in the well the cause of the abnormal operating condition lies. For example, the undesirable water production referred to above may come from one of many potential formation layers. A lack of accurate knowledge regarding the physical parameters of the well, such as this, can in turn lead to an undesirable protracted period of well inoperability or incorrect remedial action.
Accordingly, it can be seen that an improved method of determining physical parameters for characterising a well would be useful, particularly where such physical parameters could be predictively determined.